1. Field of the Invention
The present invention relates to a diaphragm valve; and more particularly relates to a weir-type diaphragm valve.
2. Brief Description of Related Art
Temperature variation and cold flow of plastic diaphragms, typically Teflon, has historically led to leaks of process media through the joint between the diaphragm and valve body. An elastomeric member, typically included in the joint to provide compensation for these variations is inadequate to prevent leakage over long periods or multiple temperature cycles.
Low friction coefficient of TEFLON® (Polytetrafluoroethylene or PTFE) material allows the diaphragm to slide between the mating flanges, radially, when the valve is cycled and thus carry process media into the crevice between the plastic diaphragm and the valve body flange.